When you’re wondering if you should use purple or blue shampoo, this is my rule of thumb caramel or darker should be blue shampoo. A light blonde to platinum blonde should be purple shampoo. The shampoo should not be used daily or every time you shampoo your hair they are there to enhance or help tone just a little bit of an unwanted underlining color out please do not use these shampoo’s daily unless you want your color to look blue or purple they will pull those colors if you use the shampoos